The present invention relates generally to fluidic transducers and more specifically to fluidic linear accelerometers.
One type of linear accelerometer is disclosed in U.S. Pat. No. 3,971,257 as including a pair of output channels to receive a jet stream in equal proportions during non-acceleration. The acceleration forces divert the jet stream to change proportion of the amount of the fluid received by the pair of outputs. Although this type of device is acceptable for most applications, it is not sensitive enough to acceleration and is incapable of measuring electromagnetic forces. Another fluidic accelerometer includes a cantilevered mass which is more sensitive in response to acceleration forces to change the output of the accelerometer. This type of device is illustrated in U.S. Pat. No. 3,201,999.
Other uses of cantilevered beams have been in electro fluidic converters as illustrated in U.S. Pat. No. 3,187,762 wherein an electromagnet creates a magnetic force transverse to the position of the cantilever beam at the nozzle to direct the fluid to one of two outlets in a digital fashion. Similarly, a cantilever bi-metallic element has been used in a fluidic amplifier to convert temperature information into a fluidic output signal as illustrated in U.S. Pat. No. 3,557,816.
Another category of fluidic linear accelerometers generally include a moving part for example, a seismic mass which deflects a jet or produces a change in resistance, capacitance, etc. or simply produces a pressure, a wave, or a flow of some kind. The main problem with each of these devices is that the moving part must slide thus creating sliding friction and coulomb friction. The sliding friction produces noise and nonlinearity and the coulomb friction produces hysteresis, distortion and noise. The cantilever devices overcome the problems of the sliding members. One of the major problems of the cantilever accelerometers of the prior art is that they are generally digital and therefore not sensitive enough to produce a linear analog response. Similarly, they have a substantially high threshold deflection. If no damping means is provided in the fluidic device, the cantilever element will ring at the resonant frequency. Although acceptable in digital on/off type of devices, this is highly undesirable in an analog force transducer. Prior art devices have not addressed themselves to this problem specifically.
Fluidic force transducers of the prior art have been individually designed to have specific threshold deflections and frequency responses. Cumbersome and inaccurate adjustments of these devices were possible. Thus, there exists a need for a force transducer which can be readily adjusted or adapted for different response ranges and threshold forces.